Nitrogen is a necessary element in the growth and development of plant life. Some plants such as legumes can take up atmospheric nitrogen and fix nitrogen into the soil. However, most plants, and in particular many plants used to produce human and animal food, require the use of nitrogen fertilizer to supply the necessary nitrogen to the plant. Nitrogen fertilizers have been, and continue to be, applied to farm fields during the various development stages of the plants. This is the case since the plant requirement for nitrogen changes during the growth and maturation of the plant. However, even with the careful application of nitrogen fertilizers, it is estimated that only about 40% to 70 percent of the nitrogen applied as fertilizer is taken up by the crop in a given year. The remaining nitrogen content of the fertilizers to which the plants are exposed is essentially lost. This then presents the challenge of how to improve the efficiency of the nitrogen fertilizers that are applied to a crop. The two ways to approach this challenge are to enhance the nitrogen feeding mechanism and to minimize the probability of nitrogen loss.
The nitrogen feeding mechanism can be enhanced by having the nitrogen present at the right place at the right time and in the right form. That is the nitrogen should be an available form in the vicinity of the root system when there is a demand for nitrogen by the growing plant. In the past this has been accomplished by various scheduled applications of fertilizer during the growing season of the plant. Slow release fertilizers have also been used. However, these techniques have not fully solved the problem.
As an example of the problem, a corn plant has about a 115 day growing period from seed to a mature plant. The need of the corn plant for nitrogen varies during this period of time. In the first 25-day period when the plant goes from the seed stage to a small plant, the nitrogen requirement is about 19 pounds per 180 bushels of corn. During the next 25-five day period as the plant grows and adds leaf material, the nitrogen demand is for about 84 pounds of nitrogen per 180 bushels of corn. During the third 25-day period, while the plant is still growing and approaching a stage of maturity when tassel and kernel formation is initiated, the nitrogen requirement is for about 75 pounds of nitrogen per 180 bushels of corn. During fourth 25-day period when there is continued kernel development and kernel growth there is a requirement for about 48 pounds of nitrogen per 180 bushels of corn. At the point of full maturity and essentially complete cob formation and kernel growth the requirement for nitrogen during the next 15-day period is for about 14 pounds of nitrogen. Consequently, it can be seen as the corn plant grows and develops its need for nitrogen is constantly changing. However, as a rule the highest demand for nitrogen by a corn plant will be at the time of tassel formation and kernel development and growth.
Nitrogen is also necessary for the growth of turf. Turf will not have as deep a root system as corn and other food plants and it therefore presents different challenges. Because of the shallow root system and the necessity for the nitrogen to be accessible to the turf root system during root growth, it is common practice to schedule a multiple number of fertilizer applications to the turf during its growing cycle. However, this is costly in both labor and fertilizer product. It is an indication that use of the fertilizer is not being maximized. It is also an indication that the applied fertilizer has a short effective availability after application. These are problems that continue to be addressed by turf producers. This is also an area where the present homogeneous granular nitrogen fertilizer exhibits distinct advantages.
The nitrogen in nitrogen fertilizers is lost after an application in various ways. When the nitrogen is applied as urea nitrogen, there is exposure to volatilization loss of nitrogen as ammonia. There is also the possibility of denitrification loss of nitrogen. In this loss, nitrate which has been applied which has been converted by soil organisms from the ammonium ion to the nitrate ion is lost through soil bacteria taking the oxygen from the nitrate nitrogen leaving gaseous nitrogen which then escapes into the atmosphere. The other loss of nitrate is through a leaching of the nitrate downwardly to below the root level of the plant. This nitrate is lost into the lower levels of the soil table or into ground water. When this nitrate enters the groundwater it is considered to be a pollutant. Consequently it is now a further objective in the use of fertilizers to have a minimum amount of the fertilizer to leach downwardly in the soil to the groundwater.
Plants including grasses, use nitrogen in the form of ammonium nitrogen and nitrate nitrogen to form amino acids which are then polymerized into proteins. The ammonium nitrogen can be taken up directly by the root system of the plant from the soil. However, nitrate nitrogen is more readily available to the root system of the plant and is more readily taken up than ammonium nitrogen in the early stages of plant growth. When nitrate nitrogen is taken up by the plant it is converted in the plant to ammonium nitrogen, then to amino acids, and then to proteins. One reason that the nitrate ion is more readily available to the plant and is more rapidly taken up by the plant is that it has a minus charge as does the clay and humus particles in the soil. Consequently, the nitrate ion is not bound into the soil. However, since the ammonium ion has a positive charge it is attracted to the clay and humus particles and is held by these particles until bacteria can cause the conversion of the ammonium ion to nitrate ion. As the ammonium ion is converted to nitrate ion it becomes available to the plant root system and is taken up by the plant. The plant root system can also take up nitrogen in the ammonium nitrogen form. Some research shows that plants prefer the ammonium form during the critical mid-season grainfill period. It is during the periods of highest nitrogen demand by a plant that the plant needs to have sufficient nitrate nitrogen and sufficient ammonium nitrogen available in the area of the root system. Although nitrate nitrogen is rapidly take up by the root system, it is considered that for maximizing the growth of a plant, and the yield from the plant that a balance of ammonium nitrogen and nitrate nitrogen is needed during periods of rapid plant growth.
The present homogeneous granular fertilizers solve many of these problems. These granular fertilizers minimize exposure to the loss of nitrogen through volatilization as ammonia. Further there is less nitrogen prone to denitrification loss and less leaching loss of the nitrogen in the form of nitrate. This is accomplished by having a large amount of the nitrogen available as ammonium nitrogen during the early stages of application. It is during these early stages of application that the plant does not have a high requirement for nitrogen. Since the nitrogen will be present as ammonium nitrogen, it will be held by the clay and humus in the soil until it can be converted to nitrate nitrogen. It is then gradually converted to nitrate nitrogen over a period of several weeks. Since nitrate nitrogen experiences the greater degree of loss, and since there is a decreased amount of nitrate nitrogen available, there is consequently a decreased loss of the nitrogen in the fertilizer through denitrification or through leaching. The result is an up to about 25 percent greater nitrogen efficiency. That is, there is an average of about a twenty-five percent increased utilization of the nitrogen that is applied to a field. In addition, there is also the factor that there is greater application flexibility. Since the nitrogen will remain in the soil and be available to the plant for a longer period of time, the fertilizer does not have to be applied to the plant in accordance with a rigorous schedule. In fact, in many instances the fertilizer can be applied once during the growing season and it will be available to the plant throughout the growing season. In addition this improved fertilizer is compatible with various herbicides which can be applied to the area in conjunction with the fertilizer.